The invention relates to a thickness shear crystal used as an overtone resonator for a quartz stabilized oscillator in the MHz range, whereby use of the resonator intended for cooperation with an essentially aperiodic oscillator circuit has been made possible without additional frequency selection means by employing specified dimension ratios of the resonator.
A resonator of this type is known from U.S. Pat. No. 4,114,062. This resonator can be operated, without additional selection means, together with an aperiodic oscillator circuit--constructed particularly in integrated circuit technology--either with the third or fifth harmonic of the resonator fundamental frequency. Therefore, in each instance, the fundamental oscillator and the third harmonic are satisfactorily suppressed during operation with the fifth harmonic, or the fundamental oscillation and the fifth harmonic are satisfactorily suppressed during operation with the third harmonic through specified dimensions of the resonator itself and its excitation electrodes.
If, however, the desired operating frequency of the resonator and the oscillator circuit lies for the third overtone of a thickness shear crystal in the relatively low frequency range of approximately 10 to 25 MHz, for example, it may result in certain applications that there is an inadequate suppression of the fifth harmonic due particularly to the integrated circuit.